Tag Archives: shipworm

A wood-boring clam inside a chunk of wood at the bottom of the ocean. Credit: Jenna Judge.

Scientists find new species of wood-munching, phallic-shaped clams

A wood-boring clam inside a chunk of wood at the bottom of the ocean. Credit: Jenna Judge.

A wood-boring clam inside a chunk of wood at the bottom of the ocean. Credit: Jenna Judge.

Some clams have evolved the ability to eat wood that makes its way to the bottom of the ocean. Remarkably, these organisms — which are the only kind besides termites that are known to digest wood — are surprisingly diverse. According to a new study, there are six different groups (genera) of wood-boring clams, comprising approximately 60 different species. Three of these genera have only been recently identified in a new study published by biologists at the Field Museum.

The termites of the sea

Like other clams, wood-boring clams have two shells covering a soft body. However, these clams also have an additional long, tube-like organ called a siphon which extends out from the shells. When the mollusk is buried deep inside a sunken piece of wood, the siphon allows the animal to pull in water and extract oxygen with the gills.

But, while their phallic appearance might elicit a chuckle, it’s their diet that makes these creatures truly interesting. The wood-boring clams flex their muscles and rock their hard shells against the wood, like a cutting tool, scraping off little bits. The clams then eat the sawdust, which they digest with the help of bacteria in their gills.  As the clams burrow, they somehow seem to know when they are near another clam’s tunnel and they avoid breaking into it, but how they are able to sense their neighbors is a puzzle.

Wood bored by shipworm. Credit: Carnegie Museum of Natural History.

Wood bored by shipworm. Credit: Carnegie Museum of Natural History.

The wood-boring clams, known as shipworms, are a centuries-old scourge to shipping activities because they weaken wooden ships and pilings. In order to keep them away, all sorts of coatings are applied to wooden ships and pilings. In the past, people used coatings that contained tributyltin (TBT), but this practice has been banned in most places around the world since TBT causes reproductive problems in aquatic organisms.

You’d think that organisms which only feed on wood aren’t that many or diverse. That’s what Janet Voight, Associate Curator of Invertebrate Zoology at the Field Museum, thought as well. But in a recent study in which Voight and colleagues studied both specimens themselves and their DNA, the researchers determined that there at least six different genera that make up the wood-boring clam family. Three of these genera have been described for the first time in the new study.

The authors also identified a completely new species lurking in one of the museum’s collections, which they named gilsonorum, in honor of the Gilsons, who have invented scientific tools and supported the museum’s efforts. The new genera have been named Abditoconus, Spiniapex, and Feaya.

Drawings showing different members of the wood-boring clam family. Credit: Lisa Kanellos.

Drawings showing different members of the wood-boring clam family. Credit: Lisa Kanellos.

“There’s not just one tree-cleaner-upper in the ocean, they’re really diverse,” Voight said in a statement. “Imagine living at the bottom of the ocean as a tiny swimming clam; you either have to find a sunken piece of wood or die. You wouldn’t think there’d be that many kinds of clams doing this. But we’ve now found that there are six different groups, called genera, and around sixty different species.”

“You think, am I seeing everything that’s there, are there cryptic species, am I over-splitting them and going crazy? It’s really scary checking yourself against the DNA, but the results matching what I found gave me a lot of confidence,” says Voight.

Close-up of one of the newly described wood-boring clams. Credit: Angelo Bernardino and Paulo Sumida.

Close-up of one of the newly described wood-boring clams. Credit: Angelo Bernardino and Paulo Sumida.

Wood-boring clams can be quite tiny, their shells no larger than a pea even as adults. However, their impact on human activities and deep-sea ecosystems can be massive when they settle in a big population.

“We have no idea how much wood is at the bottom of the ocean, but there’s probably a lot more than we think,” says Voight. “After big storms, we estimate that millions of tons of wood are washed out to sea. What if these clams weren’t there to help eat it? Think how long it would take the wood to rot. The clams contribute to the cycling of carbon, they play an integral part in making the wood into something that the other animals at the bottom of the ocean can get energy from. It could even affect sea level rise. It blows me away.”

On a related note, there are also rock-boring clams whose shells are adapted for abrasion. Unlike wood-boring clams, the rock-boring variety does not feed on rock particles — instead, it uses the rock for protection from predators.

ship-worm

Antibiotics of the future might come from the bottom of the oceans

The advent of antibiotics has spared humanity of a great deal of suffering and has saved countless lives through the years. Infectious diseases do not bore too easily and have always put out a fight, though. The bad news is that they’re winning and as the battle rages on, more and more strains become resistant to drugs. The consequences are broad and dire, and this is why scientists today want to be one step ahead and prepare for tomorrow.

Two separate studies recently published by a research partnership called the Philippine Mollusk Symbiont International Cooperative Biodiversity Group discuss how the future’s new class of antibiotics might reside at the bottom of the oceans. Like the name implies, both studies were concentrated on mollusks, a phylum of invertebrates which includes such animals as snails, clams and squid. Many of these ocean animals have been living in harmony with their bacterial companions for millions of years, and it’s in these bacteria that the key to the future’s antibiotics might lie. Having passed the test of time, rending no side effects to their animal companions, these bacteria have already shown promising results.

Ocean bacteria might be key to tomorrow’s antibiotics

ship-wormThe first study, published in the journal Proceedings of the National Academy of Sciences, the researchers tackled shipworms, but don’t let the name fool you too much. These mollusks have more to do with ships themselves than worms. Typically these are considered pests due to their ill-viewed habit of affixing themselves to the sides of wooden ships. Over time they feed on the wood, causing damage to the boat, which can be most unpleasant.

Then comes the question, however. How do these animals feed on wood? Wood is an extremely poor nutrient, far from being an ideal meal for a multicell organism, since it lacks proteins or nitrogen. Here’s the kicker though. The shipworm has a bacteria that converts the wood into a suitable food source where the animal can both live and feed. One such bacteria apparently also secretes a powerful antibiotic, which might hold great promise for combating human diseases.

“The reason why this line of research is so critical is because antibiotic resistance is a serious threat to human health,” said Margo Haygood, Ph.D., a member of the OHSU Institute of Environmental Health and a professor of science and engineering in the OHSU School of Medicine.

“Antibiotics have helped humans battle infectious diseases for over 70 years. However, the dangerous organisms these medications were designed to protect us against have adapted due to widespread use. Without a new class of improved antibiotics, older medications are becoming less and less effective and we need to locate new antibiotics to keep these diseases at bay. Bacteria that live in harmony with animals are a promising source. “

cone snailThe second paper, published in journal Chemistry and Biology, looked at cone snails collected in the Philippine. Previously, only a few studies actually were made to determine whether or not bacteria associated with these mollusks might prove useful in drug development. Mostly, this is due to the fact that cone snails aren’t that welcoming to outside visitors, featuring thick shells and quite a nasty toxic venom why they aren’t too shy about using. Since they pose a sort of miniaturized defense arsenal, it was previously assumed that these animals do not require additional chemical defense, meaning there could be no interest in human medication in turn. This was a false assumption.

Scientists proved that bacteria associated with cone snails actually produce a chemical which is neuroactive, impacting nerve cells (neurons) in the brain. Based on initial findings alone, the bacteria is already considered promising as a viable candidate for a highly powerful painkiller.

“Mollusks with external shells, like the cone snail, were previously overlooked in the search for new antibiotics and other medications,” said, Eric Schmidt, Ph.D., a biochemist at the university of Utah and lead author of the article.

“This discovery tells us that these animals also produce compounds worth studying. It’s hoped that these studies may also provide us with valuable knowledge that will help us combat disease.”